The proposed research is a continuation of the program already under way and aims to extend our knowledge on the function and possible role of the cell's second genetic system, the mitochondria, in malignancy. In most experiments, an ideally controlled cell system of chick embryo fibroblasts infected by wild-type virus, temperature- sensitive mutants, and non-transforming mutants of Rous sarcoma viruses (RSV) will be used. The origin and precursor relationships of mitochondrial DNA oligomers, as well as rates of DNA synthesis and DNA replication intermediates, will be studied at various time periods after infection and during switches between permissive and non-permissive temperatures. The base sequence complementarity of M-DNA's will be examined by hybridization and restriction endonuclease digestion. DNA methylases from mitochondrial and nuclear sources will also be characterized. Mitochondria will also be examined for messenger-like poly (A) containing RNA species. The intra-mitochondrial virus-like particles (IMV) that occur in certain RSV-induced tumor cells will be characterized and attempts will be made to influence their frequency.